Hydrothermal synthesis and characterization of a zinc-substituted gallium phosphite, [H3N(CH2)2NH3]1/2 · [GaZn(HPO3)3(H2O)2]

An organically templated zinc-substituted gallium phosphite, [H₃N(CH₂)₂NH₃]_1/2 · [GaZn(HPO₃)₃(H₂O)₂] was synthesized under mild hydrothermal conditions in the presence of ethylenediamine (en) as structure-directing agent and characterized by single-crystal X-ray diffraction analysis. It crystallizes in the orthorhombic space group Pbcn with unit cell parameters: a = 18.6146(10) Å, b = 11.0454(6) Å, c = 10.9074(4) Å, V = 2242.62(19) Å³ and Z = 8. This compound has a three-dimensional framework built up from secondary building units (SBU) of Ga(III) (or Zn(II)) and HPO₃ pseudopyramid by sharing vertices. The structure displays a two-dimensional channel system running along the [0 0 1] and [0 1 0] direction with 5-, 8- and 10-membered rings. The diprotonated ethylenediamine template molecules are located in the channels. In this structure, some of the Ga(III) sites are occupied by Zn(II) atoms. The compound was also characterized by IR spectroscopy, inductively coupled plasma (ICP), X-ray photoelectron spectra (XPS), differential thermal and thermogravimetric analyses.     

Synthesis and crystal structure of the low-spin iron(II) complex [Fe(bpz)3](ClO4)2 · H2O (bpz=2,2-bipyrazine)

The crystal structure of the title compound [Fe(bpz)₃](ClO₄)₂ · H₂O (bpz=2,2^′-bipyrazine) has been determined by a single crystal X-ray diffraction study at 293(2) K. The complex is monoclinic, P2₁/c, a=17.263(3), b=9.983(2), c=17.921(4) Å, β=107.94(3)°, V=2938.3(10) ų, Z=4, R=0.073 and R_w=0.118. The structure is made up of tris-chelated [Fe(bpz)₃]²⁺ cations, uncoordinated perchlorate anions and crystallization water molecules. The iron atom exhibits a FeN₆ distorted octahedral geometry with average Fe-N bond length and N-Fe-N bidentate angle of 1.962(5) Å and 81.6(2)°. The value of the Fe-N bond distance and that of the room temperature magnetic moment are in agreement with a singlet ¹A₁ ground state. The structure of 1 is compared to those of other tris-chelated iron(II) complexes with bidentate nitrogen heterocycles.     

Synthesis, crystal structure, magnetic properties and electrochemical behaviour of the mixed valence compound [Cu(CN)3Cu(C3H10N2)2]

The binuclear mixed valence copper(I/II) compound [Cu^I(CN)₃Cu^II(tn)₂] (1) (tn = propane-1,3-diamine) and its acetonitrile adduct [Cu^I(CN)₃Cu^II(tn)₂] · 2MeCN (2) have been synthesized. Complex 1 crystallizes triclinic, space group , a = 8.117(2) Å, b = 8.389(2) Å, c = 11.920(2) Å, α = 108.728(3)°, β = 100.024(3)°, γ = 104.888(4)°, Z = 2, and compound 2 monoclinic, space group P2₁/m, a = 8.752(2) Å, b = 13.243(3) Å, c = 9.549(2) Å, β = 114.678(4)°, Z = 2. In both crystal structures, the binuclear [Cu^I(CN)₃Cu^II(tn)₂] complex with slightly different bonding geometries is formed. One of the three nitrogen atoms of a Cu^I(CN)₃ moiety is coordinated to Cu(II) at the apex of a square-pyramid with two chelating ligands tn on its base. The shortest intramolecular Cu^II?Cu^II distance in 1 is 5.640(7) Å. The EPR behaviour of 1 has been investigated at room temperature and at 77 K. The magnetic properties were measured in the temperature range 1.8-300 K.     

Octahedral cyanohydroxo cluster complex trans-[Re6Se8(CN)4(OH)2]: Synthesis, crystal structure, and properties

A hexarhenium cyanohydroxo anionic cluster complex [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was synthesized for the first time starting from [Re₆Se₈(OH)₆]⁴⁻, which was crystallized as a salt of the composition Cs_2.75K_1.25[Re₆Se₈(CN)₄(OH)₂]·H₂O (1). The reaction of the complex with Cu²⁺ in an aqueous ammonia or methylamine solutions afforded [Cu(NH₃)₅]₂[Re₆Se₈(CN)₄(OH)₂]·8H₂O (2) or [{Cu(CH₃NH₂)₄}₂Re₆Se₈(CN)₄(OH)₂] (3), respectively. All of these three compounds were characterized by a single-crystal X-ray diffraction method. Compound 1 is crystallized in the tetragonal space group I4/m with eight formula units per cell (a = b = 17.4823(14) Å, c = 19.430(2) Å, V = 5938.3(10) Å³); compound 2 is crystallized in the monoclinic space group P2₁/n with two formula units per cell (a = 12.1845(13) Å, b = 8.6554(9) Å, c = 19.2568(19) Å, β = 91.081(2)°, V = 2030.5(4) Å³); compound 3 is crystallized in the orthorhombic space group Cmcm with four formula units per cell (a = 19.816(4) Å, b = 14.611(3) Å, c = 13.751(3) Å, V = 3981.2(13) Å³). The luminescence properties of 1 were studied in both aqueous solution and solid state. In addition, the electronic structure of [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was elucidated by DFT calculations.     

Synthesis of copper-zinc bimetallic imidazolate framework compounds and the structure of Cu(I)-containing Cu2Zn(N2C3H3)4

Copper(II)-zinc(II) bimetallic imidazolate metal-organic framework compounds of composition Cu_aZn_bIm_2(a + b) (Im = C₃H₃N₂), including Cu₂ZnIm₆ (1), were prepared in high yields from the metal oxides under mild aqueous conditions using a novel acid catalysis method. Mild acidic hydrothermal treatment of paramagnetic 1 (≥120 °C) gave diamagnetic Cu(I)-containing Cu₂ZnIm₄ (2) in high yield. The formation mechanism of 2 involves electron transfer from Im⁻ to Cu(II), with concomitant formation of the unusual cyclotriimidazole, C₉H₆N₆. Air-stable 2, characterized by single-crystal X-ray diffraction, crystallized in the tetragonal space group , with a = b = 10.9623(3), c = 6.3231(4) Å, α = β = γ = 90°, V = 759.86(6) Å³, and Z = 1.     

A novel unexpected luminescent quarternary coordination polymer {Sm3(C8H4O4)4(C12N2H8)2(NO3)}n with three high asymmetrical central Sm fragments by hydrothermal assembly

A novel chain-like luminescent samarium coordination polymer {Sm₃(C₈H₄O₄)₄(C₁₂N₂H₈)₂(NO₃)}_n (C₈H₄O₄ = phthalate, C₁₂N₂H₈ = 1,10-phenanthroline) has been assembled by hydrothermal process. The title complex crystallizes in the monoclinic system, space group P2(1)/c, with lattice parameters a = 22.56(3) Å, b = 11.155(15) Å, c = 20.32(3) Å, β = 96.70(2)°, V = 5078(12) ų, F(000) = 2964, GOF = 0.857, R₁ = 0.0358, wR₂ = 0.0597, Z = 4. Samarium ions exhibit different coordination modes from each other and lead to the unexpected high asymmetrical structure. To our knowledge, it is the first example of lanthanide coordination polymers comprising the three asymmetrical central Sm³⁺ fragments. The photophysical properties have been studied with excitation and emission spectra.     

Structure and magnetic properties of Ln2[Cu(opba)]3(DMSO)6(H2O) · (H2O) compounds with LnLa-Lu exhibiting ladder-like molecular motifs

The reaction of Ln(III) ions with the precursor [Cu(opba)]²⁻ in DMSO has afforded a series of isostructural compounds of general chemical formula Ln₂[Cu(opba)]₃(DMSO)₆(H₂O) · (H₂O), where Ln(III) stands for a lanthanide ion and opba stands for ortho-phenylenebis(oxamato). The crystal structure has been solved for the Gd(III) containing compound. It crystallizes in the orthorhombic system, space group Pbn2₁ (No. 33) with a = 9.4183(2) Å, b = 21.2326(4) Å, c = 37.9387(8) Å and Z = 4. The structure consists of ladder-like molecular motifs parallel to each other. To the best of our knowledge, this is the first Ln(III)Cu(II) coordination polymer family exhibiting the same crystal structure over the whole lanthanide series. The magnetic properties of the compounds have been investigated and the magnetic behavior of the Gd(III) containing compound was studied in more detail.     

Structure and electrochemistry of the bridging-ligand mono-substituted diruthenium compound, [Ru2(II,III)(O2CCH3)3(admpym)(Cl)(MeOH)] (Hadmpym=2-amino-4,6-dimethylpyrimidine)

The ligand substitution reaction of Ru₂(O₂CCH₃)₄Cl with 2-amino-4,6-dimethylpyrimidine (Hadmpym) under gentle refluxing conditions in methanol led to the formation of a bridging-ligand mono-substituted compound, [Ru₂(O₂CCH₃)₃(admpym)(Cl)(MeOH)] (1). Compound 1 crystallized in monoclinic space group P2₁/n (no. 14) with a=8.3074(8) Å, b=12.3722(8) Å, c=18.913(1) Å, β=95.559(3)°, V=1934.8(3) ų, and Z=4. Temperature dependence of the magnetic susceptibility of 1 revealed it to be in a spin ground state S=3/2 arising from the electronic configuration of σ²π⁴δ²(δ*π*)³. Compound 1 undergoes three metal-centered redox reactions in electrochemistry: E_1/2 ^(ox)=+0.72 V (I_a/I_c<1, ΔE_p=0.17 V); E_1/2 ^(1,red)=−0.65 V (I_a/I_c≈1, ΔE_p=0.10 V); and E_1/2 ^(2,red)=−1.80 V (I_a/I_c?1, ΔE_p=0.16 V). Then, the redox species produced by electrolysis were characterized by spectroscopic studies.     

[Hg(9-methyl-1-deazapurine)2](NO3)2 · H2O: a complex with a distorted hexagonal bipyramidal metal ion coordination sphere

Reaction of 9-methyl-1-deazapurine (9-MeDP) with Hg(CF₃COO)₂ in the presence of NaNO₃ yields the title compound [Hg(9-MeDP)₂](NO₃)₂ · H₂O with the two 9-MeDP ligands bound to the metal ion via their N7 positions. The X-ray structure is reported: monoclinic, P2₁/c (no. 14), a = 5.4015(11), b = 20.467(4), c = 17.775(4) Å, β = 97.00(3)°, V = 1950.4(7) ų, Z = 4. Hg is eight-coordinate with two trans-oriented Hg-N bonds (2.073(3) and 2.075(3) Å) and three nearly coplanar, bidentate nitrate moieties (Hg-O: 2.716(3)-2.985(4) Å), leading to a distorted hexagonal bipyramidal environment of the metal ion. Within this structure, the nitrate ions form a honeycomb-like chain structure with Hg^II being positioned inside the combs. This work represents the first report of such geometry for a transition metal ion surrounded by symmetrically bidentate nitrate ions. The corresponding nucleoside, 1-deazapurine 2′-deoxyribonucleoside, also forms a stable 2:1 complex with Hg^II, as was shown by ¹H NMR spectroscopy, making it a potential candidate for incorporation into nucleic acids based on metal-mediated base pairs.     

Preparation and structure of [Ru2(O2CMe)4]2[Fe(CN)5NO] and magnetically ordered Hx[Ru2(O2CMe)4]3−x[Cr(CN)5NO] possessing interpenetrating lattices

Reaction of [Ru₂(O₂CMe)₄]Cl with K₃[Cr(CN)₅NO] in water forms H_x[Ru^II/III₂(O₂CMe)₄]_3−x-[Cr(CN)₅NO]·zH₂O (x = 0.2) that magnetically orders at 4.0 K and possesses an interpenetrating body centered cubic [a = 13.2509(2) Å] structure with random locations of the bridging nitrosyl ligands, and x/3 vacant cation sites. Similarly, the aqueous reaction of [Ru₂(O₂CMe)₄]Cl with Na₂[Fe(CN)₅NO] forms paramagnetic [Ru₂(O₂CMe)₄]₂[Fe(CN)₅NO]·H₂O, which has a similar tetragonal interpenetrating structure [a = 13.0186(1) Å, c = 13.0699(2) Å] where the NO ligands are presumably nonbridging and 1/3 of the expected cation sites are unoccupied. The presence of uncoordinated NO sites in addition to missing neighboring [Ru₂(O₂CMe)₄]⁺ units, results in significant vacancies (or holes) in the lattice.     

Synthesis, characterization and coordination chemistry of dibenzofuran derivatives of 1,4,7,10-tetraazacyclododecane

A 1,4-disubstituted dibenzofuran derivative of 1,4,7,10-tetraazacyclododecane (cyclen), L1, has been prepared by the direct reaction of cyclen and chloroacetyldibenzofuran and the mono-substituted derivative, L2, by reaction of chloroacetyldibenzofuran and 1,4,7-tris(t-butoxycarbonyl)-1,4,7,10-tetraazacyclododecane followed by deprotection with trifluoroacetic acid. The ligands were characterized by ¹H and ¹³C NMR spectroscopy, IR spectroscopy and mass spectrometry. The reaction of the 1,4-disubstituted dibenzofuran cyclen, L1, with Cu(ClO₄)₂·6H₂O in methanol yielded crystals of [CuL1](ClO₄)₂·MeOH·1/2H₂O that were suitable for single crystal structural analysis. The X-ray structure confirmed that the 1,4-disubstituted dibenzofuran cyclen had been formed. The copper(II) coordination sphere in the complex cation, [CuL1]²⁺, is occupied by four nitrogen atoms from the macrocycle and an amide oxygen donor from one dibenzofuran pendant group. As is typical for copper(II)-cyclen complexes, the Cu(II) centre sits above the plane of the macrocycle nitrogen towards the oxygen donor, in this case by 0.5 Å. Fluorescence emission studies indicate that coordination of the macrocycle to either copper(II) or zinc(II) results in a decrease in emission with respect to the emission of the pure ligand.     

Synthesis of the donor-acceptor ligand 2-(4-dimethylaminobenzylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (dbpcd) and X-ray diffraction structure of the platinum(II) compound PtCl2(dbpcd)·1.5CH2Cl2

Knoevenagel condensation of 4-(dimethylamino)benzaldehyde with 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) gives the donor-acceptor ligand 2-(4-dimethylaminobenzylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (dbpcd). The reaction of dbpcd with PtCl₂(cod) affords the platinum(II) complex PtCl₂(dbpcd) in high yield. The free dbpcd ligand and PtCl₂(dbpcd) have been isolated and fully characterized in solution by IR and NMR spectroscopies, and the solid-state structure of PtCl₂(dbpcd) determined by X-ray diffraction analysis. PtCl₂(dbpcd), as the 1.5CH₂Cl₂ solvate, crystallizes in the triclinic space group , a = 11.7412(7) Å, b = 12.0486(7) Å, c = 14.4781(9) Å, α = 82.866(1), β = 75.049(1), γ = 83.905(1), V = 1957.6(2) Å³, Z = 2, and D_calc = 1.678 mg/m³, R = 0.0291 and wR₂ = 0.0723 for 8315 reflections with I > 2σ(I). The molecular structure of PtCl₂(dbpcd)·1.5CH₂Cl₂ consists of a square-planar platinum architecture containing two chlorines and the ancillary dbpcd diphosphine ligand. The redox properties of the dbpcd ligand and PtCl₂(dbpcd) have been explored by cyclic voltammetry, and these data are discussed with respect to extended Hückel MO calculations.     

Bifunctional chelates with mixed aromatic and aliphatic amine donors for labeling of biomolecules with the {Tc(CO)3} and {Re(CO)3} cores

A series of tridentate ligands consisting of mixed aromatic and aliphatic amine derivatives of single amino acid chelates and phenylpiperazine have been developed, and their reactions with [NEt₄]₂[ReBr₃(CO)₃] have been investigated. The compounds [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NHCH₃}]Br (4), [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NCH₃(CH₂)_xCOOC₂H₅}]Br (x = 1, 5; x = 4, 6) [Re(CO)₃{(NC₅H₄CH₂)NH(C₂H₄)N(CH₃)₂}]Br (7), [Re(CO)₃{(NC₅H₄CH₂)N(CH ₂COOC₂H₅)(C₂H₄)N(CH₃)₂}]Br (8) and [Re(CO)₃(NC₅H₄CH₂)(C₂H₄NH₂)N(CH₂)₃-CH₃Ophenpip]Br (9) (phenpip: phenylpiperazine, -C₆H₄-(CH₂CH₂)₂N-) were prepared and characterized by elemental analysis, NMR, IR, HSMS and X-ray crystallography. All complexes exhibit fac-{Re(CO)₃N₃} coordination geometry in the cationic molecular unit. Crystal data for C₁₃H₁₇BrN₃O₃Re (4): orthorhombic, Pbca, a = 13.4510(8) Å, b = 10.5728(6) Å, c = 22.5378(13) Å, V = 3205.2(3) ų, Z = 8; C₁₇H₂₃BrN₃O₅Re (5): orthorhombic, Pcca, a = 16.5907(7) Å,b = 14.8387(6) Å, c = 16.7075(7) Å, V = 4113.1(3) ų, Z = 8; C₁₃H₂₅BrN₃O₇Re (7 · 4H₂O): monoclinic, P2₁/n, a = 14.0698(17) Å, b = 9.6760(12) Å, c = 15.6099 (19) Å, β = 114.930(2)°, V = 1927.1(4) ų, Z = 4; C₁₇H₂₃BrN₃O₅Re (8): monoclinic, P2₁/n, a = 7.5312(5) Å, b = 16.0366(10) Å, c = 16.8741(10) Å, β = 98.9990(10)°, V = 2012.9(2) ų, Z = 4.     

Hydrothermal syntheses and structures of a novel zincophosphite, [C6N2H18] · [Zn3(HPO3)4]

A novel three-dimensional organically templated zincophosphite, [C₆N₂H₁₈] · [Zn₃(HPO₃)₄], was synthesized under milder hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction, differential thermal-thermogravimetric analysis, powder X-ray diffraction, ³¹P MAS NMR spectrum, and IR spectroscopy. It crystallizes in the monoclinic system, space group C2/c with cell parameters: a = 8.7820(4) Å, b = 14.9417(7) Å, c = 15.4943(5) Å, β = 92.940(2)°, and Z = 4. The structure consists of a network of strictly alternating ZnO₄ tetrahedra and pseudo-pyramid, forming 4-membered ring chains. The structure has a 4.8.16-net and 8- and 16-membered ring channels where completely protonated N,N,N′,N′-tetramethylenediamine cations are encapsulated. The structure is stabilized by template-to-framework hydrogen bonding. In phosphites system, this compound possesses extra-large-pores.     

Synthesis, characterization and magnetic properties of a novel fluorinated iron phosphite Fe2(HPO3)F2 with infinite -Fe-F-Fe-O-Fe- linkage and -Fe-F-Fe- layer

A novel fluorinated iron phosphite Fe₂(HPO₃)F₂ (1) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma (No. 51) with a = 7.3458(15) Å, b = 10.038(2) Å, c = 5.4947(11) Å, V = 405.16(14) Å³, Z = 4. Its structure is built up from iron(II) oxygen-fluorine FeO₃F₃ octahedra and HPO₃ pseudo-tetrahedra, giving rise to a 3D inorganic framework. The infinite -Fe-O-Fe-F-Fe- linkage and -Fe-F-Fe- layer in the framework are the noteworthy structural features. Mössbauer spectrum shows the presence of Fe²⁺ in the octahedral coordination. Magnetic measurements indicate the existence of antiferromagnetic interactions.     

Synthesis and characterisation of palladium(II) iodo complexes containing water soluble phosphine ligands. Crystal structures of [PdI2(PTA-H)2][PtI3(PTA)]2 · 2H2O and trans-[PdI2(PTA)2]

The aqueous solution behaviour of the equilibrium related cis-[PdCl₂(PTA)₂] and [PdCl(PTA)₃]Cl complexes has been investigated in the presence of acid and iodide ions. Several of the resulting species were identified and a reaction scheme accounting for identified complexes is proposed. The crystal structures of trans-[PdI₂(PTA-H)₂][PdI₃(PTA)]₂ · 2H₂O (1) (PTA-H⁺ = protonated form of PTA) and trans-[PdI₂(PTA)₂] (2) are reported. The geometry around the Pd(II) metal centre in 1 (for both the cation and anion) and 2 is distorted square planar. The PTA ligands occupy a trans orientation in the cation of 1 and in complex 2. Compound 1 represents a rare example of a Pd(II) system wherein the cation:anion pair, in a 1:2 ratio, are both coordination complexes. It is the first d⁸ Ni-triad square planar complex containing only one PTA ligand and only the second platinum group metal complex. For the cation in 1, the bond distances and angles are Pd(1)-P(1) = 2.2864(16) Å, Pd(1)-I(1) = 2.6216(7) Å, P(1)-Pd(1)-P(1)′ = 180.00(7)° and P(1)-Pd(1)-I(1) = 87.62(4)°, while in the anion the bond distances are Pd(2)-P(2) = 2.2377(15) Å, Pd(2)-I(4) = 2.5961(13) Å, Pd(2)-I(2) = 2.6328(13) Å, Pd(2)-I(3) = 2.6513(8) Å, while the angles are P(2)-Pd(2)-I(4) = 90.00(5)°, P(2)-Pd(2)-I(2) = 89.69(5)°, I(4)-Pd(2)-I(2) = 179.57(2)°, P(2)-Pd(2)-I(3) = 175.19(4)°, I(4)-Pd(2)-I(3) = 90.29(4)° and I(2)-Pd(2)-I(3) = 90.05(4)°. Bond distances and angles of the coordination polyhedron in 2 are Pd-P = 2.327(3) Å, Pd-I = 2.5916(10) Å, P-Pd-I = 89.13(7)° and P-Pd-P = 180.00(13)°. The average effective- and Tolman cone angles for the two ligands, calculated from the crystallographic data, are 115° and 117° for PTA and PTA-H, respectively.     

Hydrothermal synthesis, structure characterization and catalytic property of a new 1-D chain built on bi-capped Keggin type mix-valence molybdenum compound: (NH4)[Mo6Mo6O36(AsO4)Mo(MoO)]

The synthesis and structure of a new 1-D molybdenum-arsenic compound based on the bi-capped Keggin anion [Mo^VI₆Mo^V₆O₃₆(AsO₄)(Mo^VO)₂]⁻ have been reported, and its catalytic property has been examined. The title compound was characterized by IR, TG and X-ray diffraction analysis. Single crystal X-ray diffraction shows that it crystallizes in cubic crystal system, space group Pn-3m with cell dimension: a = 11.749(2) Å, V = 1622.0(5) Å³, Z = 2. Its structure has a 1-D infinite chain, in which the bi-capped Keggin anions are connected by sharing one terminal oxygen atom from the caps. The compound shows a moderate styrene conversion (48%), the major product for the oxidation of styrene is benzaldehyde (85.2%).     

A nearly symmetric trinuclear chromium(III) oxo carboxylate assembly: preparation, molecular and crystal structure, and magnetic properties of [Cr3O(O2CPh)6(MeOH)3](NO3) · 2MeOH

Complex [Cr₃O(O₂CPh)₆(MeOH)₃](NO₃) · 2MeOH (1 · 2MeOH) has been synthesized from the one-pot reaction between Cr(NO₃)₃ · 9H₂O and NaO₂CPh in MeOH. The structure of the complex has been solved by single-crystal X-ray crystallography. It crystallizes in the monoclinic space group P2₁/n with a=14.716(6) Å, b=22.569(8) Å, c=15.755(6) Å, β=95.02(1)°, V=5212.5(4) ų and Z=4. Although the cation does not possess any crystallographically imposed symmetry element, its {Cr₃(μ₃-O)} core is nearly symmetric. Each Cr^III…Cr^III vector is further bridged by two η¹:η¹:μ₂ benzoates, with a terminal MeOH molecule completing octahedral coordination at each metal ion. The crystal structure consists of layers that are parallel to (0 1 0) crystallographic plane and are formed through π-π stacking interactions and hydrogen bonds. Variable-temperature magnetic susceptibility and solid-state ¹H NMR studies indicate that the total spin value of the ground state is 1/2. EPR experiments reveal the existence of a distribution of trimers with axial anisotropy in the g tensor.     

Polymorphism and weak antiferromagnetic interactions in dibromo[(−)-sparteine-N,N]copper(II)

Two polymorphic crystal structures of the title compound, dibromo[(−)-sparteine-N,N^′]copper(II), 1, were determined. The structures of two isomorphs of 1, 1a [orthorhombic, P2₁2₁2₁, a=11.0463(9) Å, b=11.9839(15) Å and c=12.7835(19) Å] and 1b [orthorhombic, P2₁2₁2₁, a=7.6779(9) Å, b=12.0927(14) Å and c=18.090(2) Å], are composed of the same basic structural unit, Cu(C₁₅H₂₆N₂)Br₂. The bond distances in the molecular structures of 1a and 1b are identical to each other within the esds. However, there are slight differences in the bond angles around the Cu(II) center and considerable differences in their packing structure. Crystal 1a exhibits weak anti-ferromagnetism (J=−1.89 cm⁻¹) as opposed to the magnetically isolated paramagnetism observed for the analogous dichloro[(−)-sparteine]copper(II), 2. The results of a magneto-structural investigation of 1a and 2, and other supporting evidence, suggest that the pathway for the weak antiferromagnetic super-exchange in 1a might be through a Cu-Br ? Br-Cu contact.     

Hydrothermal synthesis and structure of a Cu(I) bromide coordination polymer, [(tpyprz)3Cu10Br10] (tpyprz = tetra-2-pyridylpyrazine)

The hydrothermal reaction of CuBr₂ and tpyprz in the presence of NH₄VO₃ and HF for 72 h at 170 °C provided [(tpyprz)₃Cu₁₀Br₁₀] (1) in 20% yield. The two-dimensional structure of 1 may be described as Cu(I)-tpyprz chains, linked through {Cu₄Br₅}⁻ clusters in the ac-plane and decorated with {Cu₃Br₅}²⁻ clusters projecting from one face of the layer in the b-direction. The Cu(I) sites exhibit distorted trigonal coordination {CuBr₃} and distorted tetrahedral geometries, {CuBr₂N₂} and {CuN₄}. Crystal data for 1: monoclinic space group C2, a = 12.7561(8) Å, b = 19.359(1) Å, c = 15.860(1) Å, β = 97.178(1)°, V = 3885.8(4) Å³, Z = 2, D_calc = 2.222 g cm⁻³, μ(Mo Kα) = 78.75 cm⁻¹.